MOSCOW (AP) — Russia's prime minister sternly warned the United States against ramping up sanctions, saying Friday that Moscow would retaliate with economic, political and unspecified "other" means.

The tough message from Prime Minister Dmitry Medvedev marked what the Kremlin sees as a red line, reflecting growing dismay with announced U.S. sanctions that have sent the Russian ruble plummeting to its lowest level in two years.

The U.S. State Department said Wednesday that Washington would impose new sanctions this month after determining this week that Moscow used a military grade nerve agent in March to poison an ex-Russian spy in England. Russia has strongly denied involvement in the poisonings of Sergei Skripal and his adult daughter.

According to the State Department, the sanctions will include the presumed denial of export licenses for Russia to purchase many items with national security implications.

New sanctions proposals in the U.S. Congress include legislation targeting Russia's state-controlled banks and freezing their operations in dollars — a move that would deal a heavy blow to the Russian economy.

Medvedev warned the U.S. that such a move would cross a red line.

"If something like a ban on bank operations or currency use follows, it will amount to a declaration of economic war," the Russian prime minister said. "And it will warrant a response with economic means, political means and, if necessary, other means. Our American friends should understand that."

Foreign Minister Sergey Lavrov told U.S. Secretary of State Mike Pompeo during a telephone call Friday that the new sanctions were "categorically objectionable," according to a Russian Foreign Ministry statement.

Medvedev's tone differed considerably from the nonchalant ones President Vladimir Putin and his lieutenants have used when talking about Western sanctions and downplaying their impact on the Russian economy.

Word of more U.S. sanctions has rattled the Russian currency and stock markets. The ruble dropped about 1.5 percent in Friday trading to 67.78 to the dollar, its lowest level since August 2016.

Russia-U.S. ties have sunk to their lowest level since Cold War times amid tensions over Ukraine, the war in Syria and the allegations of Russian meddling in the 2016 U.S. presidential election.

Moscow's hopes for better ties with Washington under President Donald Trump have withered as his administration has introduced waves of sanctions against Russia.

Medvedev said that while the U.S. describes the restrictions are punishment for Russia's "bad" behavior, he thinks the real goal is to sideline a rival.

"It's intended to remove Russia as a strong competitor on the international arena," he said.

Medvedev pointed at U.S. efforts to block the planned construction of a new Russian natural gas pipeline to Germany in order to encourage the sales of American liquefied natural gas to Europe as an example of "unfair competition."